Influenza virus encodes a large, multidomain RNA-dependent RNA polymerase that can both transcribe and replicate the viral RNA genome. In influenza virus, the polymerase is composed of three polypeptides: PB1, PB2 and PA/P3. PB1 houses the polymerase active site, whereas PB2 and PA/P3 contain, respectively, cap-binding [1] and endonuclease domains required for transcription initiation by cap-snatching [2]. This entry represents the CAP binding domain [2].

1: Recombinant-baculovirus-expressed PB2 subunit of the influenza A virus RNA polymerase binds cap groups as an isolated subunit. Shi L, Galarza JM, Summers DF; Virus Res 1996;42:1-9. PMID:8806170

2: Crystal structure of the RNA-dependent RNA polymerase from influenza C virus. Hengrung N, El Omari K, Serna Martin I, Vreede FT, Cusack S, Rambo RP, Vonrhein C, Bricogne G, Stuart DI, Grimes JM, Fodor E; Nature. 2015;527:114-117. PMID:26503046